Download
the source code for the latest XFC development release:

Download the
latest libsigc++ 2.0 source code:

You can clone a working copy of the
latest XFC source code from the the GIT repository:

git clone git://git.xfce.org/bindings/xfc

Please note that a "working copy" of the XFC source code is quite large
because it contains the hidden administrative subdirectories (.git)
Git uses to keep the working copy in sync with the repository.